Galactic Gamma‐Ray Background Radiation from Supernova Remnants

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Abstract
The contribution of the source cosmic rays (SCRs), confined in supernova remnants, to the diffuse high-energy γ-ray emission above 1 GeV from the Galactic disk is studied. Gamma-rays produced by the SCRs have a much harder spectrum compared with those generated by the Galactic cosmic rays that occupy a much larger residence volume uniformly. SCRs contribute less than 10% at GeV energies and become dominant at γ-ray energies above 100 GeV. The contributions from π0-decay and inverse Compton γ-rays have comparable magnitude and spectral shape, whereas the bremsstrahlung component is negligible. At TeV energies the contribution from SCRs increases the expected diffuse γ-ray flux by almost an order of magnitude. It is shown that for the inner Galaxy the discrepancy between the observed diffuse intensity and previous model predictions at energies above a few GeV can be attributed to the SCR contribution.
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